Transient developmental expression of IgY and secretory component like protein in the gut of the axolotl (Ambystoma mexicanum).

Julien S Fellah ,S Iscaki ,Jean-Pierre Vaerman ,Jacques Charlemagne

doi:10.1155/1992/21679

Abstract

We previously reported that a primitive vertebrate, the Mexican axolotl (Amphibian, Urodela) synthesizes two classes of immunoglobulins. IgM are present in serum early in the development, and represent the bulk of specific antibody synthesis after an antigenic challenge. IgY occur in the serum later during the development, and are relatively insensitive to immunization. We demonstrate in the present work, using immunofluorescence with specific Mabs, that IgY are expressed in the gut epithelium, as secretory molecules. Secretory IgY are well expressed in the stomach and intestinal mucosae of young animals from 1 month after hatching to the seventh month. Thereafter, IgY progressively disappear from the gut and become readily detectable in the serum of 9-month-old preadult immunologically mature animals. Axolotl IgY are closely associated in the gut to secretory component-like (SC) molecules that are well-recognized by antisera to the SC of different mammalian species. This is the first description, in a primitive tetrapode, of an immunoglobulin class that could be the physiological counterpart of mammalian IgA.

Highlights

Protection of the mammalian gastrointestinal mucosae against pathogenic agents largely depends on nonimmune factors such as pH, enzymatic secretions, mobility of the glandular epithelium, and mechanical properties of the epithelial mucus
We demonstrate in the present work, using immunofluorescence with specific Mabs, that IgY are expressed in the gut epithelium, as secretory molecules
In stomach sections of young axolotls (1 month after fertilization), a bright staining occurred in the cytoplasm of large cells located in the lamina propria near the basal side of enterocytes (Fig. 1, panels 1 and 2)

Summary

Introduction

Protection of the mammalian gastrointestinal mucosae against pathogenic agents largely depends on nonimmune factors such as pH (gastric acidicity), enzymatic secretions (proteases, peroxidase, lysozyme), mobility of the glandular epithelium, and mechanical properties of the epithelial mucus (reviewed in Pabst, 1987). The barrier function of the gut consists in lymphoid cells, either organized in lymphoid structures such as Peyer’s patches, or dispersed in the epithelium (intraepithelial lymphocytes, IEL). Secreted IgA molecules consist of IgA-dimers covalently linked to a J chain and associated to a glycoprotein, the secretory component (SC) (Tomasi et al, 1965; Lemaitre-Coelho et al, 1977a; Kihn and Kraehenb(ihl, 1979). SC is the extracellular moiety of a transmembrane receptor (the Poly-Ig receptor) that allows cytoplasmic translocation of IgA (and IgM) from the basolateral to the apical side of enterocytes and the secretion of the translocated molecules in the digestive lumen (Brandtzaeg, 1973, 1981; Nagura et al, 1979). The Poly-Ig receptor is encoded by a gene belonging to the Ig gene superfamily (Mostov et al, 1984)

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Conclusion